Railway train communication system



vINVENTORS Paal/Vamm Feb. `1, 1949. w. l.. KONRAD ET AL RAllLWAYV TRAIN COMMUNICATION SYSTEMv Filed Dec. 12, 1944 Nl wm IHK/2 ATTORNEY @SVN @Aviv mw. i.

Nu. Mm

Patented Feb. l, 1949 worth, Pa.; assignors to The- Union Switch and SignalA Company, Swissyale, Pa., a corporation of Pennsylvania f Application .December 12, 13 44, Serial No. 567,844

` Claims;

. 1. Our inventionv relates to railway train communication systems, v

Y Several methods of'providing communication between-spaced railway vehicles and between suchvehicles 'and fixed' points have' b'eenproposed. In train communication continuity lof service at all points along the railway and underv all Weather conditions is essential. .That is, communication must not be lost d ue to curves,.cuts, tunnels, bridges. and vnearby facto-ry buildings, or due to storms. lurthermore, a high .signal to noise'ratio is required because of. the noiseof a train in motion, andof the noise created due to stray magnetic elds, false currentsand other electrostatic conditions. Also, the service should be confined to the railway right-o-f-way, so that there is privacy in the communication. .,Again, systems using .apparatus requiringnogovernment .license or assignment of wave bands are desirable.

In. view of. the foregoing circumstances, a feature of ,our invention is the provision of improved railway train communication apparatus.

Anotherfeature of our invention is the provision of improved railway train communication apparatus for utilizingfthe track rails and existing line wires and'other conductorsparalleling the f track as a channel. throughwhich .cor-nimunication current is transmittedand guided. along the railway. Y Stilly anotherfeaturefof our .invention is the provision. of improvedy railway train .communicationapparatus tov minimize noise.

,.Aga'im a` feature of .our invention isthe-.provision of improved irailway .train communication apparatus which substantially confines-its influ ence to therailway right-ofway,. andr whichV apparatus requires no wave band license.. .Other features, `objects and advantages .embodying .our invention will appear aslthe .specification progresses.

.The general featuresofour invention. are obtained throughthe provision of train carried elements disposed for the transfer of electrical energy .between such. elements and the track rails and. other conductors parallelingthe track.` The current used is such that therails and paralleling conductors through their Idistributed impedance toY .ground and distributed .inductance-capacitance, serve as a channel throughl 'whicn'the current is guided along the trackway, the channel being madeI up of a plurality of paths each Iof which adds something to the sum total ofthe transmission. At some points. along the railway,

the track rails may bethe` more effective portion of the channel,.and at. other points the existing paralleling line wires and otherl conductors may be the more effective portion of the channel. Furthermore, the current used is such that it is largely conned tov this channeland its influence extends vonly for short distances at right angles to the track. To minimize the noise We provide transmitting and receiving .apparatus which utilizes frequency'n'lodulation, the frequency of the carrier being preselected to be substantially free from interference with otherN systems and to be suitable to eiect transmission and reception with a relatively low energy output.

We shall describe onev formof apparatus embodying our invention, 'and shall thenpoint out the'novel features thereof in claims.

The accompanying drawing is a diagrammatic View showing lone form of railway traincommunication apparatus embodying our invention.

Referring tothe drawing, the reference characterV CO represents a railway train vehicle on Vwhich two--way communication apparatus embodying our invention isinstalled. This vehicle CO may be, for example, a Caboose of a freight train, andthe apparatus installed thereon includes transmitting apparatus and receiving apparatus which are indicated as a whole by the reference characters TA and RA, respectively.

The caboose COv is provided with a source of power ,whichY is shown as a motor generator MG, the motor l of which is supplied'with current by any-suitable means, such as an axle driven generator andjstorage battery of the commonV 32 volt car lighting system the terminals of such current source being indicated inthe drawing as B32 and N32. Generator 8 of the motor generator MG supplies power at a voltage suitable for use with vacuum` tubes of the transmitting and receiving apparatus to be described shortly. The positive and negative terminals of the generator G are .indicated in the drawing` as B330 and N3ll, respectively, the terminal Nlb` being connectedto a .ground electrode 9 which may be the metalframeof the caboose. l

` The cabOOse CO has mounted thereon sending and receiving elements through which energy is transferred between the train carried apparatus and the trackway communication channel. The sending element to transfer energy between the transmitting apparatus TA and the trackway channel comprises a loop circuit LC and a coil SC. The loop circuit LC includes a wire 2 connected to a pair of wheels 4 at one end of the caboose, condenser Ci, and wire 3 connected to a pair of wheels at the other end of the Caboose. The circuit LC is completed between these two pairs of wheelsthrough the track rails. In the drawing only one rail of the track and only one wheel of each of the pairs of wheels are shown for the sake of simplicity. To conne such loop circuit, the two pairs of wheels 4 and 5 are preferably insulated from the body of the caboose.- Such insulation may be of diierent constructions and is indicated conventionally by insulation IN between each truck and the caboose body. This insulation may be, for example, insulation placed at the journal bearings in the manner covered by Letters Patent of the United States No. 2,064,- 642, granted December 15, 1936 to Paul N. Bossart for Railway train communication Systems. The connection of wires 2 and 3 to the respective pair of wheel may be through terminals secured to the ends of the journal bearing brasses as disclosed in the above-mentioned BossartV patent, there being preferably a connection to the journal bearing brass of each wheel of each pair of wheels to insure a balanced condition. It is to be noted, however, that this insulation may be eiected by insulating one truck or one pair of wheels and insulating the front draw bar of the caboose, the draw bar insulation being provided to avoid a shunting of the current through the cars of a train to which the Caboose is attached,

The sending coil SC is preferably a rectangular shaped air core coil suspended from the floor of the Caboose. In practicing the invention the coil SC would preferably be made up of two coils, one over each rail, and the two coils connected together to add their effects.

It is clear that the loop circuit LC is a coil of one turn having inductive relationship with coil SC and that periodic current supplied to coil SC induces a corresponding electromotive force in the loop circuit causing current to flow therein and vthus create a corresponding voltage drop i across the rails between the spaced pairs of wheels 4 and 5. The capacitance CI tunes the loop circuit to the frequency band of the communication current to increase the flow of current. The major portion of the impedance of this loop circuit is the impedance of the rails and thus the voltage drop across the rails between the two pairs of wheels represents the major portion of the power consumed. The voltage drop across this length of the rails causes current to ilow through the rails in multiple to each side of the caboose and through the distributed rail to ground imped-V ance, the current being of a relatively large magnitude near the Caboose and attenuated to a relatively low magnitude at points remote from the vehicle. The relatively large current flowing in the rails near the Vehicle induces an electromotive force in existing line wires, such as line wire LW. and other parallel conductors due to the mutual inductance between the rails, circuits SC and LC and such conductors. The line Wire electromotive force in turn causes current to flow in such line wires due to the distributed capacitance of the line wires to ground, and at point remote from the vehicle the current owing in the line Wires is relatively large compared to that remaining in the rails with the result that the current in the line wires induces electromotive forces in the rails due to the mutualinductance between the line Wires and the rails. This last mentioned electrornotive force in turn causes current to then low in the rails due to the distributed rail to ground impedance. That is to say, the trackway channel includes the rails, existing line wires and other conductors paralleling the tracks, and such channel serves to transmit and guide the communication current along the right of way. This trans mission of current is explained more fully in the aforementioned Bossart patent and reference is made thereto for a full understanding of the transmission of communication current along such a trackway channel` The receiving element of Caboose CO for picking up energy from the trackway channel is an air core coil RC mounted in a vertical plane on the top of the Caboose. In this position the coil RC is disposed to pick up an electroinotive force when'a periodic current flows in the trackway channel.

The transmitting apparatus TA, the output of which is connected to the sending coil SC, coinprises as essential elements a microphone Ml, a frequency modulating means, and one or more stages of amplification. The modulation means comprises a tube Vl 4and an oscillator tube V2, together with the necessary circuits and sources of power. The amplifying means comprises two stages of amplification, including tubes V3 and V4 although it is clear that the number of stages may be more or less than those shown. The several vacuum tubes of the transmitting apparatus may be of any suitable type and indirectly heated pentodes are shown, the filament of Veach tube being heated in any convenient manner.

Tube VI is provided with a control grid circuit, including control grid It, reactance coil ll, secondary winding l2 of a transformer biasing unit BUI and cathode I3; and with an anode circuit extending from terminal B2i-iii) of the source of power through front Contact iii of a relay DRI, to be Lreferred to later, wire 2&3, re-

sistor |32, reactance coil 2l, anode 2E: tube space to cathode i3 of tubeV Vi, unit Elli, and ground electrodes i8 and S to Yternunal ci the source of power. Primary winding lei oi the transformer Tl is interposed in 'a microphone circuit comprising microphone Ml, battery i5, primary winding E4, ground electrodes i8 and E, front contact l1 of relay DRE, and wire iii. It

. follows that voice frequencies created in the microphone MI are applied to the control grid lil of tube Vl through the transformer Tl and corresponding Variations in the anode current are produced. A gas tube Vt of the cold cathode type is preferably connected to the anode circuit and serves as a voltage regulator. v

Oscillator tube V2 has associated therewith an oscillating circuit comprising an inductance coil 23, two capacitors 2d and 25 and resistor 2E. Capacitor 24 in series with resistor 2G and the combination in multiple with capacitor 2liV are connected across the coil 25. One terminal of this oscillating circuit is connected to control grid 21 of tube V2 througha unit BUZ and its other terminaljis connected to ground electrode 3l. An intermediate terminal of coil 23 of the oscillating circuit is connected to cathode 28 of tube V2 to form with the irst two grids oi tube V2 the well-known Hartley oscillator circuit. VAn anode voltage supply circuit for tube V2 which steed-e541 functionsas1 anelectron.' coupled oscillator"is"Y formed from:terminal-:B389 of' ther power source through-iront'contactfIS--of relayDR-A, wire 20, resistor 29:; anodel'il and-tubespacetocathode 28;A intermediate: terminal' and` lower portionv off ine duct'an'ce"4 coil 23' andground: electrodes 31,-' and 9"? toy terminal NSM; G'ol Zdarid'capacitor 251v are" sol-'proportionedthatl t sci-llations'fgeneratedby the' cathode) and' theiirs 'two grids oftube'VZ' are oia' preselected carrier requency;i-. andi-'by way of' illustrationVi and: to aid man .understanding-or our invention; we' shall: assume that' a: carrierf ol?A 85 kilocycles 'per sec'ondisgeueratedt lt isi tu be 'understoodthatv our iiuentionfis notv limitedtol this carrier rreduency an'dotner fre-v quencies-oan lie-"used:` .rer,.tnefcarrier'fre quency is preferably pr `lected-wtorprovid eincien-t transfer 'of' energy' through metallic cori'-V 'Ihe tube Vl is'. coiuolfe'tl toithe'-oscil-latingcirLA cuit through capacitorsI and C3 aridi.conse#V quen'tiyf voicefrequency# current applieuftotube Vif causs- Ghs` tb appear as" a- Changifrfg capacity across capacitor zelo-ff the" oscillating: circuit and" the* frequency created thereby'- is varied;- That is' tofsay ,tli`e tube Viti-'serves as a variablerea'ctance' throlig-hv which" the carrieifis irequenc'yf'nfodulated-1in.accordance vliith tl'fievl'c'eV freuuencies". f

Auipliie'rl tubel V3'- is' provided-f u'tith2 a= control grid circuit comprisingy oontrolf'grid aaresistorf 33;; biasingflunit Blf-I3 a'nfd cathode 342; and-'With an anode.V circuit-i exten-ding front terminal-'IBEW through.' front contentr le or relay DRI?, wire: zu, primary vv'irrclirig-l 35' 0iV a; trarisfo'im'er' 'Ii-2g aulo e`v-A ing` unit BUIii and cathodefdll; and-Wi-tli 'an anode circuit' receiving currentfro-ini terr''oin"al`V B390! through front contact? t9 of relay-"DRI, vi/'iif'eZiJ-jl winding el, anode-elifan'dftube spa'catolcathode unit BH4- and ground-electrodes 4-3iand5`to terminal N311-ll. It follows that the" amplified frequency modulatedtelephone current is fur-r theramplified at-tube VL. t

The anode circuit of tubev V4 is coupled to the sending'coil, SC through. a capacitancefl, winding 45 and capacitance [0d in multiple andg'round'el'ectro'de 98j Thus'tle frequency mo'du-- iated' carrier` te1epnon'e' current as empiinedl by tube/VB is supplied to the'sen'rig' coilL SCtb" de transferred to the 'trackway channelv irl, tliemari ner already explained-Lv The receiving' apparatus-RA includesV as-` essen-'- tial elements-an'- amlolil'ler RMI?, ai limi-ter includl ingfavvacuum tube V5;l a discriminatorincludingv is connected to the" amplierinV series withr a capacitance 93,another capacitor 34 being-'connected across the' secondary winding 92; Resistor 95 is connected across the input of' amplifier AMI'. The output sideof amplier'AMl coupled to the control grid and cathode ill of limiter tube V5 through a transiorrner'T; as willv be readily understood by an inspection of the' drawing. Tube V5 is shown as an indirectly heated pen-Y tode having an anode circuit suppliedl with current from terminal Blle through back Contact 48 of relay DRE, reactance coil t9, Wire' 5u; r'e' `sisters 5l and 52, Winding 53 oi a coupling trans# former T5, anode 5d and tube space to cathode-4l' and ground electrodes anda to terminalNSllll The parts are so proportioned' that 'tube V5' is provided with a relatively low anode voltage and functions to linut the amplication of thevr oscillations applied to the control grid ofA the tube through the amplifier AMI. Thus the' oscillaAN tions picked up by the receiving coil PUC are ree produced in the output of the lin'iiter tube VE at substantialy vuniform amplitude.

The anode circuit of tube V5 includes/a tuned circuit comprising capacitor Cl', resistor'l' and' winding 53 of transformer T5, and thisv tuned circuit is coupled to another tuned circuit includ'- ing capacitor C8, resistor 65 and' Winding' 5B oil transformer T5. These two circuits are tuned to resonance at substantially the carrier frequency; The outside terminals of the tuned circuit includ-l ing Winding 5S are connected' to the anodes` dland 58 of discriminator ktube Vii, tube Vt be'ingl a duodiode type of' tube. Mid terminal oiseaondary winding 55 is connected through aninduct'# Y ance coil Sl'to thejunction terminal of' resistors 52 and 53, the outside'terininals of'which resistors' arev connected to .the cathodesl 5t and lili, respec' tively, of the ltwo sections of tube Vt'. .Cerise quently, a resultant direct voltagevaryiug'in amd plitude according to the frequency` variation' of the' energy applied to the tuned' circuits ape a vacuum tube V6, and two audio amplify-ingA pears acrossthe resistors S2 and Amplifier tube Vl is a triode'having aff-control' grid circuit including resistor till 'and a' biasing unit BUE, -a'ndwhich grid circuit is coupledy to resistorsZ- and 5-3-y ofthe discriminator*througha capacitor C5. Thus the direct voltage variations appearing across the resistors 62-and f'ifare ap l plied to the control grid circuit of tube Vl andV cause corresponding variations in the amplitude oi` the anode circuit current of this tube, and which anode circuit receives power vfrom terminal B3B!) through back contact #i3 of relay DRI, coil- 49, wire 5c, resistor lili, anode' 5'? and' tube space to cathode 5S; unit and ground electrodes 55 and 9 to terminal Neill);

The' secondsta'ge amplifier tube' V8 is of the pentone type, and its control grid 52'- coupled tothe' anode circuit oftube V'l/y throughV capacitor CB, and the anode current variationsoi ti-ibe' V1 are further amplied-by the tube VS ih the usual manner'. A couplingtransformer liasf aprim'arywinding 'l5-'interposed inthe anode' cir-f cuitofvtubel/'B and a" secondary Winding 'ifi' cluded'in'a circuit fora loud speaker LS, .this'loud speaker! circuit being completedA through back'- contact 12 of relay DRl and ground 'electrodes B? and 13a 1 i Normally] that is, with relay-*Dl-tl--re'lease ',-1

cuits of its various tubes being deenergized and the microphone circuit being open. In describing the operation of the system of the apparatus, it is to be understood, of course, that apparatus similar to `that provided for caboose CO is mounted on another vehicle of the train or at some wayside station and that communication is effected between these two points through the medium of the trackway channel.

If a communication current consisting of a. preselected carrier frequency modulated by the voice frequency is picked up 4by coil RC at caboose CO, such current is amplified at the amplifier AMl, any variation in the amplitude of the current is limited at the limiter tube V5., the frequency variations of the current are reproduced as variations in amplitude of a direct voltage by the discriminator and such direct voltageV variations are amplified at tubes Vl and V8, and the voice frequencies which the direct voltage variations represent are reproduced at the loud speaker LS. If the trainman in the caboose wishes to reply to such received speech or if he wishes to initiate a conversation, he depresses a push button PB to complete a simple circuit for energizing relay DRI and that relay on picking up switches the power source from the anode circuits of the receiving tubes to the anode circuits of the transmitting tubes, and serves to energize the microphone circuit. Speaking into the microphone MI causes corresponding variations in the frequency of the carrier supplied through the oscillator tube and such frequency modulated carrier after further amplification is applied to the communication channel of the trackway to eect the receiving apparatus at the remote office. From this point on, proper operation of the push button PB to switch from sending to receiving conditions permits the caboose to carry on a conversation with the remote station.

Train communication apparatus here disclosed has the advantages that the communication current is transmitted and guided along the trackV and loss of communication due to curves, cuts and other conditions is avoided. Secrecy of communication is obtained because'of the confining of the communication current to substantially the right of way. Noise is minimized because of the modulation used and arrangement of'apparatus. Furthermore, relatively simple and inexpensive apparatus is required.

Although we have herein shown and described only one form of railway train communication systems embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what We claim is:

l. In combination, a railway train vehicle having mounted thereon transmitting apparatus operable to supply a periodic current of a given frequency, a closed single turn secondary circuit on said vehicle connected to spaced pairs of wheels of the vehicle to include a portion of the track rails in the circuit and completed through capacitance to tune the circuit to the frequency of said periodic current, said secondary circuit being characterized by the impedance of the rails being a major part of the circuit impedance, and a primary circuit on the vehicle including an air core coil mounted within said secondary circuit for mutual inductance with said secondary circuit and connected to said transmitting apparatus to cause such periodic current to fiow in the rails.

2. In combination, a railway train vehicle havingY mounted thereon transmitting apparatus operable to supply a periodic current of a preselected frequency band, a closed secondary circuit including a conductor extending lengthwise of the vehicle and each end of which conductor is connected to a pair of wheels at the respective end ofthe vehicle to include a given length of the track rails in the circuit, a capacitor included in series with said conductor to tune the secondary circuit to resonance at the mean frequency of said frequency band, a primary circuit including an air core coil mounted withinsaid secondary circuit Vfor mutual inductance to both the rails and said conductor of the secondary circuit, and said primary circuitV connected to said transmitting apparatus to transfer said periodic current due to the mutual inductance of said coil with said conductor and track rails.

3. In combination, a railway train vehicle having mounted thereon transmitting apparatus operable to supply a given periodic current, a closed secondary circuit including a low impedance conductor extending lengthwise of the Vehicle through a capacitor and having each end connected to a pair of wheels at the respective end of the vehicle to include a portion of the track rails in the circuit, said secondary circuit characterized by one side being formed solely by said conductor and capacitor for the rails in the other side of the circuit to form the major portion of the impedance of the circuit and the voltage drop across such portion of the rails is a large percentage of the total voltage drop of the circuit when periodic current ows therein, a primary circuit including a large air core coil mounted 0n the vehicle for mutual inductance'with said secondary circuit, and said primary circuit connected to said transmitting apparatus for transfer of said periodic Vcurrent to the track rails through said secondary circuit.

4. `In combination, a railway track along which a line wire extends, the rails of said track and said line Wire forming a transmitting channel for periodic current due to their distributed mutual inductance and distributed impedance to ground, a railway train vehicle having mounted thereon transmitting apparatus capable of supplying periodic current of a preselected frequency band, an air core coil connected to said transmitting apparatus, a single turn sending loop circuit having one side formed by a conductor extending lengthwise of the vehicle between two spaced pairs of wheels of the vehicle and the other side formed by the rails in multiple between said two pairs of wheels, a capacitor interposed in said conductor to tune the sending circuit for said frequency band, and said air core coil mounted on the vehicle within the sending circuit for mutual inductance with the sending circuit and said line wire for transfer of the periodic current ofthe transmitting apparatus to said transmitting channel. Y

5. In combination, a railway track along which a line wire extends, the rails of said track and said line wire forming a transmitting channel for periodic current due to their distributed mutual inductance and distributed impedance t-o ground, a railway train vehicle having mounted thereon transmitting apparatus capable of supplying periodic current of Va given frequency band, an air core coil connected to said transmitting appa- 9 ratus, a single turn sending loop circuit including REFERENCES CITED the track rails in multiple between two spaced pairs of wheels of the vehicle and a conductor exh? ftcgwleferences are of record m. the tending lengthwise of the vehicle between said p two pairs of wheels, and said air core coil mounted 5 UNITED STATES PATENTS on the vehicle between; said conductor and the Number Name D track rails for inductive relation to the conductor 2 064 642 Bossart Dec '5te1936 and rails of said sending loop circuit and to the 2273090 Crosby 1"* Feb 17 1942 line wire for transferv of said periodic current 2286997 Hunt m Jun'e 16 1942 frorn the transmitting apparatus to said trans- 10 316:351 Fosternn: Alm 20 1943 mttmg channel' 2,344,699 Hunt Mar. 21, 1944 WILLIAM L KONRAD. 2,379,395 Ziegler et al. June 26, 1945 PAUL N'. BOSSAR'I'I OTHER REFERENCES CHARLES E' LEBERKNIGHT- 15 May 1942 issue of Electronics, pages 56 and 119. 

